{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU6126-4FB1","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU6126-4FB1","canonicalUrl":"https://aoctrl.com/siemens/3RU6126-4FB1","factsUrl":"https://aoctrl.com/api/mcp/products/3RU6126-4FB1","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS thermal overload relay, 3RU6126-4FB1, adjustable 34-40 A, Trip Class 10, size S0, screw terminals for main and auxiliary circuits, stand-alone installation.","salesMarkdown":"Its adjustable current response range of 34 to 40 A means you set the trip threshold to match the motor's full-load current — the relay then protects against sustained overcurrent by heating a bimetal strip that trips the contactor. Trip Class 10 means it will trip within 10 seconds at 7.2× the set current, which is the standard for standard-duty induction motors (pumps, fans, compressors) that don't need the slower Class 20 or the faster Class 5. This relay is a stand-alone unit (not a clip-on module) with screw-type terminals for both the main and auxiliary circuits. It occupies the S0 contactor footprint — the same frame size as the 3RT102 contactor series — so it bolts directly to the contactor or mounts separately on the DIN rail. The 45 mm width and 95 mm depth keep the panel fill factor tight; you need 6 mm clearance to grounded parts on each side. The relay carries a substance prohibitance date of 05/01/2012, indicating RoHS compliance from that date. The operating frequency is 50/60 Hz, and the rated operational current is 40 A. For documentation, expect a Siemens declaration of conformity covering IEC/EN 60947-4-1 (the standard for electromechanical contactors and motor-starters).","metaTitle":"Siemens 3RU6126-4FB1 Thermal Overload Relay, 34-40 A, Class","metaDescription":"Siemens SIRIUS 3RU6126-4FB1 thermal overload relay, adjustable 34-40 A, Trip Class 10, size S0, screw terminals, current lifecycle stage. Sourced to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"95 mm","Width":"45 mm","title":"3RU6126-4FB1","Height":"97 mm","at 24 V":"2 A","Per Pole":"3.2 W","at 110 V":"0.22 A","at 230 V":"2 A","Trip Class":"CLASS 10","description":"Overload relay 34...40 A size S0, class 10, for motor protection stand-alone installation main circuit: screw terminal AUX. circuit: screw terminal manual automatic reset","lifecycle_stage":"current","During Operation":"-40 ... +70 °C","During Transport":"-55 ... +80 °C","Fastening Method":"stand-alone installation","Mounting Position":"any","Solid Or Stranded":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)","Product Brand Name":"SIRIUS","Product Designation":"Thermal overload relay","For Main Current Circuit":"screw-type terminals","power loss [W] total typical":"7.5 W","Operating Voltage Rated Value":"690 V","Substance Prohibitance (Date)":"05/01/2012","Design Of The Overload Release":"thermal","Operating Frequency Rated Value":"50 ... 60 Hz","Operational Current Rated Value":"40 A","for AWG cables for main contacts":"2x (16 ... 12), 2x (14 ... 8)","For Auxiliary And Control Circuit":"screw-type terminals","Relative Humidity During Operation":"0 ... 90 %","Surge Voltage Resistance Rated Value":"6 kV","for AWG cables for auxiliary contacts":"2x (20 ... 16), 2x (18 ... 14)","Finely Stranded With Core End Processing":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)","Number Of Poles For Main Current Circuit":"3","shock resistance according to IEC 60068-2-27":"8g / 11 ms","Required Spacing For Grounded Parts At The Side":"6 mm","Size Of Contactor Can Be Combined Company-Specific":"S0","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Arrangement Of Electrical Connectors For Main Current Circuit":"Top and bottom","Tightening Torque For Main Contacts With Screw-Type Terminals":"2 ... 2.5 N·m","insulation voltage with degree of pollution 3 at AC rated value":"690 V","power loss [W] for rated value of the current at AC in hot operating state":"9.6 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"34 ... 40 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/ccd0dec60fa210936e46be261cac0c3f.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=621550&mlfb=3RU6126-4FB1"},"ai":{"faq":[{"question":"What is the closest functional second-source — 3RT1023-1AL20?","answer":"The 3RT1023-1AL20 is a contactor, not an overload relay — it is the matching contactor for the S0 frame size. The 3RU6126-4FB1 is the overload relay that pairs with that contactor. They are complementary, not substitutes."},{"question":"What is 3RU6126-4FB1's listed depth?","answer":"The depth is 95 mm."},{"question":"What is 3RU6126-4FB1's listed width?","answer":"The width is 45 mm."},{"question":"Will 3RU6126-4FB1 drop into a panel specified around 3RT1023-1AL20 without rewiring?","answer":"Yes — both are size S0, so the overload relay bolts directly to the contactor or mounts on the same DIN-rail footprint. The screw terminals accept the same wire gauges (2x 0.5-1.5 mm² and 2x 0.75-2.5 mm² solid/stranded). No rewiring is needed if the contactor is already wired for the motor circuit."},{"question":"What compliance documentation does Siemens provide for 3RU6126-4FB1?","answer":"RoHS compliance is confirmed from 05/01/2012. Expect a declaration of conformity covering IEC/EN 60947-4-1. The relay is rated for 690 V insulation at pollution degree 3 and 6 kV surge voltage."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU6126-4FB1","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3RU6126-4FB1 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}